1. Field of the Invention
The present invention relates to a method for inhibiting the enzyme protein kinase C by amphipathic long-chain bases such as sphingosine and sphinganine. The invention further relates to compositions capable of producing inhibition of protein kinase C. Inhibition of protein kinase C is useful in a variety of ways. Such inhibition can lead to inhibition of the oxidative burst in neutrophils, whereby an anti-inflammatory effect is achieved. Inhibition of protein kinase C can also lead to inhibition of differentiation and growth of cells and can thereby produce an anti-tumor effect.
2. Description of the Related Art
Phospholipid/Ca.sup.+2 -dependent protein kinase (protein kinase C) is a major protein phosphorylation system which was first found in brain (Takai et al, J. Biol. Chem. 252, 3692, 1977) and subsequently shown to occur widely in tissues and phyla of the animal kingdom (Kuo et al, Proc. Natl. Acad. Sci. U.S.A. 77, 7039, 1980). Protein kinase C plays an important role in signal transduction, cellular differentiation, tumor promotion and neurotransmission. The central function of protein kinase C in transducing intracellularly extracellular signals has recently been recognized (Nishizuka, Nature 308, 693, 1984). Extracellular agents including neurotransmitters, hormones, and growth factors are bound by specific cell surface receptors and elicit, by transmembrane signalling, the generation of two second messengers by stimulating the degradation of phosphatidylinositols (Nishizuka, Philos. Trans. R. Soc. Lond. B. Biol. Sci. 302, 101, 1983; Michel, Trends Biochem. Sci. 4, 128, 1979; and Berridge, Biochem. J. 220, 345, 1984). In particular, the inositol phospholipid phosphatidylinositol-4-5-bisphosphate (PIP.sub.2) is hydrolyzed to inositol triphosphate (IP.sub.3) and sn-1,2-diacylglycerol (DAG) (Nishizuka, Science, 225, 1365, 1984). DAG activates protein kinase C. Phorbol-diesters, which are potent tumor promoters, also activate protein kinase C (Castagna et al, J. Biol. Chem. 257, 7847, 1982). In fact, it appears that protein kinase C is the phorbol-diester receptor (Niedel et al, Proc. Natl. Acad. Sci. U.S.A. 80, 36, 1983) and mediates most, if not all, of the biological effects of the phorbol-diesters.
Recently, protein kinase C has been shown to be inhibited by a lipoidal amine, 4-aminomethyl-1-[2,3-(di-n-decyloxy)n-propyl]-4-phenylpiperidine dihydrochloride (CP-46, 665-1) in human leukemic cells (Shoji et al, Biochem. Biophys. Research Comm., 590, 1985). This amine has also been shown to have anti-metastatic properties in rodent tumor models (Wolff et al, Cancer Immunol. Immunother., 12, 97, 1982). This study supports the connection between inhibition of protein kinase C and anti-cancer activity, such as in human chronic myelogenous leukemia and other similar types of cancer, and is hereby incorporated by reference in this application.
Dyson and Montano have reported an anti-tumor agent which is a sphingosine derivative (J. Am. Chem. Soc., 100, 7441, 1978), but protein kinase C was not implicated.
Several other types of inhibitors of protein kinase C have also been reported. These include calmodulin antagonists (Mori et al, J. Biol. Chem. 255, 8378, 1980; Wise et al, J. Biol. Chem. 257, 8489, 1982; and Robinson, J. Cell. Biol. 101 1052, 1985), H-7 (Hidaka, Biochemistry 23, 5036, 1984), adriamycin (Wise, J. Biol. Chem. 257, 8489, 1982); alkyllysosphospholipid (Helfman, Cancer Res. 43, 2955, 1983), a non-steroidal anti-estrogen, tamoxifen (O'Brien, Cancer Res. 45, 2462, 1985), amiloride (Besterman, J. Biol. Chem. 260, 1155, 1985), verapamil (Mori et al, J. Biol. Chem. 255, 8378, 1980), bilirubin (Sano, Ped. Res. 19, 587, 1985), palmitoylcarnitine (Nakadate, Cancer Res. 46, 1589, 1986), gangliosides G.sub.M1, G.sub.D1a, G.sub.D1b and G.sub.T1b (Kim, J. Neurosci. Res. 0109 15, 159, 1986), and retinal (Patarroyo, Immunobiology (Stuttgart) 170, 305, 1985). These various inhibitors of protein kinase C have widely varying potencies, and some are specific whereas others are non-specific.
In order to fully appreciate the present invention relating to inhibition of protein kinase C, it is necessary to understand other related work relating to the activation of protein kinase C. Such activation has been associated with tumor growth, and it is also believed that oncogenes may somehow affect the degree of activation of protein kinase C.